In this position the tsumego seems to be clear. So the black has to kill the white and a way to do this is to make a connection but not to play on the critical point. So with the connection we can see it as the edge of the goban, the black can ensure his position and force in fact the white to connect after the hane and the two stones but at the end to avoid another eye at the corner, black plays in the corner the connection is forced and at the end we have black who kills the white.